From our research, your trailer(and ours) was made in January of 1948
shortly after the Airstream production was moved from the LA Metro airport to the North Main Street factory. If you go to vintageairstream.com and select the Model Resources Tab and select the Tab for the 1947 Liner it will give you the explanation of the VIN tags. By Serial #1200 the VIN Tags were changed to an oval brass tag and the Model numbers were dropped from the tag. If you select the Tab for the 1948 Liner you will see that the Serial numbers for 1948 ranged from around #1090 and ended around #1280 at the end of the year. I think a November produced trailer would probably have had a brass oval VIN tag and would not have had the Model number. Hope this information was helpful.